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From: antonio@qualcom.qualcomm.com (Franklin Antonio)
Newsgroups: alt.sys.sun,comp.dcom.lans
Subject: Re: Cabletron Repeater Problems
Message-ID: <1991Jun24.000210.4759@qualcomm.com>
Date: 24 Jun 91 00:02:10 GMT
References: <1991Jun20.075328.6540@qualcomm.com> <1991Jun20.203445.12130@unhd.unh.edu> <1991Jun21.212938.29822@usenet.ins.cwru.edu>
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In article <1991Jun21.212938.29822@usenet.ins.cwru.edu> lim@po.CWRU.Edu writes:
>>>In article <1991Jun20.075328.6540@qualcomm.com> antonio@qualcom.qualcomm.com (Franklin Antonio) writes:
>>>
>>>isolate problems to a particular port?  We've recently implemented
>>>Remote-Lanview ...
>>>unreliable, all this provides is a very fancy Windows program to display
>>>random numbers.  I expect these statistics should be a TOOL i can use to
>
>  You are not asking too much.  Remote-Lanview(PCOV) has helped me solve
> many problems on our network.  It is great to have those statistics on
> every single port...

Thank you for this report.  Now that we know that the Cabletron statistics
CAN work, we just have to figure out how to make them work for us.


>>>... we use one repeater port for EACH Shiva
>>>FastPath.  ...  We still
>>>get lots of collisions on these ports, sometimes 10% or 15%...
>
>  What do you mean by 10% to 15 %?  PCOV give the collision percentage as
>%port/Board and %Port/MMAC on the IRM.  The defination of the %Port/MMAC
>is the percentage of collisions of which the port is responsible, based on 
>total MMAC activity.

I just look at the total number of collisions reported for a port, and
divide by the number of packets on that port.  We often have these numbers
in the 10% to 15% range on Cabletron repeater ports which have nothing
but a single Shiva FastPath on them.   


>>>discovery.  We can reduce the number of collisions by choosing WHICH
>>>ports we use for the Shiva FastPaths...

>  It make perfect sense here.  If you put less devices on the THN-MIM port
>the less collision percentage it will display on the PCOV.  You you have done
>is using more ports on you THN-MIM at the same time, you have just distribute
>the collision packet transmission per port.  The total collision percentage
>of the THN-MIM bord still remain the same but the percentage per port will be
>much smaller now - see the defination.

I guess i didn't make myself clear enough.  We dedicate one Cabletron
repeater port to each Shiva FastPath, even tho the FastPath's are only
about 2ft away from the repeater.  These particular Cabletron repeater
ports have one each Shiva FastPath, and _nothing_ _else_ on them.

Now, given that, which ports on the MMAC should i use?  Are all repeater
ports created equal?  If i pull some cables from the front of the THN-MIMs
and plug them in different ports -- this is _just_ a _permutation_ of ports!
-- i would expect all the collision statistics to remain the same.
(of course now reported on different port numbers, because i have moved
the "interesting" traffic to different repeater ports)
What we seem to have discovered is that all repeater ports are _not_ 
created equal.  The worst choice seems to be to plug those cables from
the FastPaths into ports all on one THN-MIM card.  Still one repeater
port per FastPath, and nothing else on those ports.  The best choice seems
to be to plug the cables from the FastPaths into ports chosen one per
each THN-MIM card.  Still one repeater port per FastPath, and nothing else
on those ports.  This doesn't make sense at all for any reasonable 
functioning of the repeaters.

No way will i believe that permuting the cables at the front panel of
the repeater should change the performance of my network.

Thanks again for your thoughts tho.  I'm pleased to know that someone
is haveing good luck with Cabletron's repeaters.  I was beginning to 
think we just made a really bad decision when we decided to go with them.

I still have my network problems... and i'm still interested to hear
from anyone who has Shiva FastPath boxes successfully working with
Cabletron repeaters.